1. Field
The present embodiment relates to a threaded safety fastener that prevents the fastener from becoming completely disengaged from a threaded surface.
2. Prior Art
This embodiment relates to threaded fastening methods, specifically to threaded nut fasteners where complete disengagement of a threaded fastener may cause undesirable results. The present applicant developed this embodiment to prevent a threaded fastener, used for adjusting a motorized mechanism, from becoming completely disengaged from a threaded adjusting rod when loosening. If the threaded adjusting fastener where allowed to become completely disengaged from the adjusting rod, the motorized mechanism would fall, possibly causing injury and damage. A method was needed to prevent the threads of the adjusting fastener from fully disengaging the threads of the adjustment threaded rod when coming to the end of the threaded rod's threads.
In view of these problems, an object of the present embodiment is to provide a dual safety fastener assembly whose constituent fastener can surely be loosened without concern for complete disengagement from the threads it engages.
The present embodiment describes a fastener, split in two, thereby having a first fastener and a second fastener. The threaded bore of the first fastener is centered coaxially as is the threaded bore of the second fastener. The force for adjusting the double fastener assembly is applied to one fastener, commonly done with a wrench or by hand. Importantly, the embodiment functions operationally the same regardless of which fastener torque is applied to, in other words, either the first fastener or second fastener. However, for clarity, the description is for that in which torque is applied to the second fastener. To transfer the force from the second fastener to the first fastener, a protrusion in the first fastener is coaxially aligned with a pivotable recess in the second fastener. The protrusion of the first fastener extends from the bottom side of the first fastener, fitting into the recess of the top side of the second fastener. The first fastener protrusion and second fastener recess share a common axis. It is noted that the protrusion and recess share a common axis. The first fastener's threaded bore and second fastener's threaded bore, only share a common axis when both are engaged with a threaded rod. The recess diameter in the second fastener is slightly larger than the cylindrical protrusion of the first fastener, allowing the protrusion to pivot within the recess. It is important to note that the second fastener can only transfer torque to the first fastener when both first and second fasteners threaded bores are engaged with the threaded rod.
Importantly, the first fastener protrusion and second fastener recess are axially aligned, and are adjacent to their respective threaded bore centers. The concentric pivot point for the first fastener protrusion and aligning second fastener recess resides between the outer parameter of their respective fastener and centered threaded bore. It is further noted that a slight space exists between the adjoining first fastener and second fastener where there surfaces abut.
The threaded bores are centered unto themselves for both the first fastener and second fastener. The axis for the first fastener and second fasteners threaded bores are centered to each other only when the first fastener and second fastener threads are concurrently engaged with a common threaded rod. It is also noted upon loosening the constituent second fastener; its threads will be first to completely disengage from the threaded rod leaving the first fastener as the means of support for the mechanism being adjusted. Any further attempt to disengage the first fastener causes the second fastener to swing away from the first fastener in an eccentric manner, pivoting on the common axis of the first fastener protrusion and second fastener recess. It is further noted that when the second fastener is completely disengaged from the threaded rod, the first fastener and second fastener are still attached by the first fastener protrusion and second fastener recess. Any further attempt to disengage the first fastener by applying rotational torque to the second fastener will cause the second fastener to encircle eccentrically the first fastener on their shared axis thus eliminating any rotational torque to the first fastener.
It is important to note that the second fastener can reengage the threaded rod after being disengaged from the threaded rod. With sufficient pressure on the second fastener, rotated in the direction to engage the threaded rod, the second fastener will swivel until the first and second fasteners threaded bores are coaxially aligned. Once both fasteners are aligned concentrically, the second fasteners threads will catch the beginning thread of the threaded rod causing the second fastener to engage the threaded rod's threads. Once both fasteners are engaged, adjustment to a device supported by the threaded rod can once again proceed.
U.S. Pat. No. 6,609,867 to Wakabayashi (2002) shows an upper nut and lower nut that engage with each other in an eccentric manner to afford the so-called wedging effect of inhibiting them from loosening themselves. While effective in preventing the constituent nuts from loosing, they afford no advantage from complete disengagement from a threaded rod once loosened. Furthermore, the wedging, or binding of threads ultimately causes excessive wear and weakens the threaded surface reducing their effectiveness. Further, the fastener is overly complex and expensive to manufacture.
Another radical attempt to prevent a fastener from loosening includes U.S. Pat. No. 4,220,187 to Holmes (1980). Here the inventor uses a skewed or deformed fastener to put lateral pressure against the threads, potentially weakening and shearing away the threads of the fastener. Furthermore the design affords no advantage when loosened to prevent complete disengagement from a threaded surface.
U.S. Pat. No. 3,908,727 to Osborne (1975) is another attempt to prevent a fastener from loosening, including applying deformable materials on the threads to prevent them from loosening thereby potentially causing the fastener to gum up and jam. Here the design offers little advantage over applying an aftermarket liquid to the threads to prevent loosening. Furthermore the design affords no advantage when loosened to prevent complete disengagement from a threaded surface.
Like the almost innumerable embodiments for threaded fastener that claim anti-loosening properties, the designs afford no advantage when loosening to prevent complete disengagement from a threaded surface.